Cryogenic containers are specifically designed and made of
materials that can withstand the rapid changes and extreme temperature
differences encountered in working with liquid nitrogen. Even these special
containers should be filled slowly to minimize the internal stresses that occur
when any material is cooled. Excessive internal stresses can damage the
container.

Do not ever cover or plug the entrance opening of any liquid
nitrogen dewar. Do not use any stopper or other device that would interfere
with venting of gas.

These cryogenic liquid containers are generally designed to
operate with little or no internal pressure. Inadequate venting can result in
excessive gas pressure which could damage or burst the container. Use only the
loose-fitting necktube core supplied or one of the approved accessories for
closing the necktube. Check the unit periodically to be sure that venting is
not restricted by accumulated ice or frost.

Use proper transfer equipment

Use a phase separator or special filling funnel to prevent
splashing and spilling when transferring liquid nitrogen into or from a dewar.
The top of the funnel should be partly covered to reduce splashing. Use only
small, easily handled dewars for pouring liquid. For the larger, heavier containers,
use a cryogenic liquid withdrawal device to transfer liquid from one container
to another. Be sure to follow instructions supplied with the withdrawal device.
When liquid cylinders or other large storage containers are used for filling,
follow the instructions supplied with those units and their accessories.